Fluorine-Free Tungsten ALD And Tungsten Selective CVD For Dielectrics

ABSTRACT

Methods of forming metallic tungsten films selectively on a conductive surface relative to a dielectric surface are described. A substrate is exposed to a first process condition to deposit a fluorine-free metallic tungsten film. The fluorine-free metallic tungsten film is exposed to a second process condition to deposit a tungsten film on the fluorine-free metallic tungsten film.

The present application claims the benefit of priorities to U.S. Provisional Appl. No. 63/034,721, filed Jun. 4, 2020, which is hereby incorporated by reference in its entirety.

TECHNICAL FIELD

Embodiments of the disclosure pertain to the field of electronic device manufacturing, and in particular, to an integrated circuit (IC) manufacturing. In particular, embodiments of the disclosure pertain to methods for filling surface structures with a metal containing film.

BACKGROUND

Integrated circuits are made possible by processes that produce intricately patterned material layers on substrate surfaces. Producing patterned material on a substrate requires controlled methods for deposition of desired materials. Selectively depositing a film on one surface relative to a different surface is useful for patterning and other applications.

Conventional methods for metal deposition frequently suffer from poor selectivity to dielectric surfaces. Additionally, single wafer process environments can suffer from low throughput for atomic layer deposition (ALD) processes.

In high-k metal gates with FINFET schemes, the features that need to be filled are getting extremely small as the technology node goes to 14 nm and below. Tungsten hexafluoride (WF₆) based chemical vapor deposition (CVD)/ALD tungsten films introduce fluorine and cannot be directly deposited on the gate without a barrier layer and a nucleation layer. As the dimensions of the electronic devices shrinks, the barrier layer and nucleation layers occupy most of volume in narrow feature. The high resistivities of these films impact the performance of the resultant device.

Therefore, a need exists for improved methods for selective metal deposition.

SUMMARY

One or more embodiments of the disclosure are directed to methods for depositing a tungsten film. In some embodiments, the method comprises exposing a substrate surface to a first process condition comprising a flow of a fluorine-free tungsten precursor and a flow of a first reducing agent to form a fluorine-free metallic tungsten film on the substrate surface to a first thickness, and exposing the fluorine-free metallic tungsten film to a second process condition comprising a flow of a second tungsten precursor to deposit a tungsten film.

In some embodiments, the method comprises exposing a substrate surface to a first process condition comprising a flow of a fluorine-free tungsten precursor and a flow of a first reducing agent to form a fluorine-free metallic tungsten film on the substrate surface to a first thickness, treating the fluorine free metallic tungsten film with a plasma, and exposing the plasma treated fluorine-free metallic tungsten film to a second process condition comprising a flow of a second tungsten precursor to deposit a tungsten film.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above recited features of the present disclosure can be understood in detail, a more particular description of the disclosure, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this disclosure and are therefore not to be considered limiting of its scope, for the disclosure may admit to other equally effective embodiments. The embodiments as described herein are illustrated by way of example and not limitation in the figures of the accompanying drawings in which like references indicate similar elements.

FIG. 1 shows a cross-sectional schematic view of a semiconductor device during a process method in accordance with one or more embodiment of the disclosure;

FIG. 2 shows an exemplary process method according to one or more embodiment of the disclosure; and

FIG. 3 shows a cross-sectional schematic view of a semiconductor device during a process method in accordance with one or more embodiment of the disclosure.

In the appended figures, similar components and/or features may have the same reference label. Further, various components of the same type may be distinguished by following the reference label by a dash and a second label that distinguishes among the similar components. If only the first reference label is used in the specification, the description is applicable to any one of the similar components having the same first reference label irrespective of the second reference label.

DETAILED DESCRIPTION

Before describing several exemplary embodiments of the disclosure, it is to be understood that the disclosure is not limited to the details of construction or process steps set forth in the following description. The disclosure is capable of other embodiments and of being practiced or being carried out in various ways.

A “substrate” as used herein, refers to any substrate or material surface formed on a substrate upon which film processing is performed during a fabrication process. For example, a substrate surface on which processing can be performed include materials such as silicon, silicon oxide, strained silicon, silicon on insulator (SOI), carbon doped silicon oxides, amorphous silicon, doped silicon, germanium, gallium arsenide, glass, sapphire, and any other materials such as metals, metal nitrides, metal alloys, and other conductive materials, depending on the application. In some embodiments, the substrate comprises titanium nitride (TiN), titanium aluminide (TiAl), tantalum nitride (TaN), silicon (Si), tungsten (W), tungsten carbo nitride (WC_(x)N_(y)), cobalt (Co) or combinations thereof. Substrates include, without limitation, semiconductor wafers. Substrates may be exposed to a pretreatment process to polish, etch, reduce, oxidize, hydroxylate, anneal and/or bake the substrate surface. In addition to film processing directly on the surface of the substrate itself, in the present disclosure, any of the film processing steps disclosed may also be performed on an under-layer formed on the substrate as disclosed in more detail below, and the term “substrate surface” is intended to include such under-layer as the context indicates. Thus, for example, where a film/layer or partial film/layer has been deposited onto a substrate surface, the exposed surface of the newly deposited film/layer becomes the substrate surface.

As used in this specification and the appended claims, the terms “precursor”, “reactant”, “reactive gas” and the like are used interchangeably to refer to any gaseous species that can react with the substrate surface.

As used herein, the term “liner” refers to a layer conformably formed along at least a portion of the sidewalls and/or lower surface of an opening such that a substantial portion of the opening prior to the deposition of the layer remains unfilled after deposition of the layer. In some embodiments, the liner may be formed along the entirety of the sidewalls and lower surface of the opening.

One or more embodiments of the disclosure are directed to high selectivity deposition processes. Some embodiments have high deposition rates for metal fill applications. Some embodiments use fluorine-free metal precursors to increase selectivity and deposition rate. Some embodiments provide high selectivity fluorine-free tungsten deposition with high throughput ALD processes. Some embodiments incorporate a reducing agent in the first ALD process to increase the selectivity relative to dielectrics and increase the deposition rate with comparable film performance (e.g., step coverage, gap filling). In some embodiments, the fluorine-free tungsten film throughput is increased due to increased deposition rate of the fluorine-free tungsten precursor.

Some embodiments of the disclosure provide atomic layer deposition methods incorporating a reducing agent in the first ALD step. Without being bound by any particular theory of operation, it is believed that the inclusion of the reducing agent enables the precursor to thermally decompose into different derivatives of the precursor with significantly greater precursor reduction in the main reducing ALD step.

One or more embodiments of the disclosure incorporate different gases (e.g., H₂, SiH₄, Si₂H₆, Si₄H₁₀, NH₃) into the metal (e.g., tungsten (W)) precursor dose. In some embodiments, the incorporation of a reducing agent improves the selectivity of the metal deposition relative to dielectrics and accelerates the rate of metal reduction.

ALD Fluorine-Free Tungsten (FFW) in some embodiments replaces and/or reduces traditional high resistivity nucleation layers (e.g., SiH₄ or B₂H₆ ALD W 20-30 Å) and thick fluorine barrier (e.g., TiN 30-50 Å). In some embodiments, FFW has low resistivity, excellent step coverage, superior fluorine barrier property, and can integrate with conventional WF₆ based bulk W fill. Some embodiments improve throughput while maintaining acceptable film performance or other metrics (e.g., non-uniformity, step coverage, particles).

One or more embodiments of the disclosure are directed to methods with high deposition rate Fluorine-Free Tungsten. A small co-flow of a reducing agent, like H₂, SiH₄, Si₂H₆, Si₄H₁₂, NH₃, is added to the Fluorine-Free Tungsten precursor ALD dose step. In some embodiments, the growth of Fluorine-Free Tungsten film with a hydrogen (H₂) co-flow by ALD occurs at a suitable temperature (e.g., ranging from 400° C. to 550° C., or form 460° C. to 475° C.).

The Fluorine-Free Tungsten precursor for growing Fluorine-Free Tungsten film includes, but is not limited to, tungsten chloride and hydrogen as reducing agent. In some embodiments, Fluorine-Free Tungsten film is grown on a conductive layer (e.g., TiN or TiAl films). In one or more embodiments, the ALD process includes: exposure to a Fluorine-Free Tungsten dose with 50-500 sccm of H₂ co-flow, purge, H₂ dose, purge. Argon (Ar) or other suitable inert gas is used for precursor carrier and purging in some embodiments.

In some embodiments, the deposition rate of the Fluorine-Free Tungsten film is increased 2× or more on TiN and TiAl films. In some embodiments, the film throughput is increased due to increased deposition rate of the Fluorine-Free Tungsten precursors. In some embodiments, a Fluorine-Free Tungsten nucleation layer is deposited followed by high deposition rate Fluorine-Free Tungsten film in same chamber without air break.

In one or more embodiments, the small amount of reducing agent (H₂) with Fluorine-Free Tungsten precursor does not show any CVD W film growth. Without being bound by any particular theory of operation, it is believed that without enough reducing agent, the W precursor is not reduced completely to metallic W. It is further believed that with small amount of reductant, some of W precursor reduces to different W precursor derivatives that are less reactive and are not readily reduced to metallic W with low H₂ flow. The tungsten precursor derivatives deposited on the substrate surface is reduced to metallic tungsten.

Referring to FIGS. 1 through 3, one or more embodiments of the disclosure are directed to methods 200 for depositing metal films 140 on a substrate 100.

FIG. 3 illustrates the method 200 depositing the metal film 140 on the substrate 100; for example, a blanket deposition process.

FIG. 1 shows the substrate 100 having at least one feature 112 formed therein. Those skilled in the art will understand that the single feature 112 shown in FIG. 1 is for illustrative purposes and there can be more than one feature. The shape of the feature 112 can be any suitable shape including, but not limited to, peaks, trenches and cylindrical vias. In specific embodiments, the feature 112 is a trench. In other specific embodiments, the feature 112 is a via. As used in this regard, the term “feature” means any intentional surface irregularity. Suitable examples of features include, but are not limited to trenches which have a top, two sidewalls and a bottom, peaks which have a top and two sidewalls extending upward from a surface, and vias which have sidewalls extending down from a surface with an open bottom. Features can have any suitable aspect ratio (ratio of the depth of the feature to the width of the feature). In some embodiments, the aspect ratio is greater than or equal to 2:1, 4:1, 5:1, 10:1, 15:1, 20:1, 25:1, 30:1, 35:1 or 40:1. In one or more embodiments the aspect ratio is in a range of from 2:1 to 40:1, from 2:1 to 35:1, from 2:1 to 30:1, from 2:1 to 25:1, from 2:1 to 20:1, from 2:1 to 15:1, from 2:1 to 10:1, from 2:1 to 4:1, from 4:1 to 40:1, from 4:1 to 35:1, from 4:1 to 30:1, from 4:1 to 25:1, from 4:1 to 20:1, from 4:1 to 15:1, from 4:1 to 10:1, from 5:1 to 40:1, from 5:1 to 35:1, from 5:1 to 30:1, from 5:1 to 25:1, from 5:1 to 20:1, from 5:1 to 15:1, from 5:1 to 10:1, from 10:1 to 40:1, from 10:1 to 35:1, from 10:1 to 30:1, from 10:1 to 25:1, from 10:1 to 20:1, from 10:1 to 15:1, from 15:1 to 40:1, from 15:1 to 35:1, from 15:1 to 30:1, from 15:1 to 25:1, from 15:1 to 20:1, from 20:1 to 40:1, from 20:1 to 35:1, from 20:1 to 30:1, from 20:1 to 25:1, from 25:1 to 40:1, from 25:1 to 35:1, from 25:1 to 30:1, from 30:1 to 40:1, from 30:1 to 35:1 or from 35:1 to 40:1. In one or more embodiments the aspect ratio is greater than 10:1.

The substrate 100 illustrated in FIG. 1 includes a first material (conductive material 104) with a first surface (conductive surface 105) and a second material (dielectric material 106) with a second surface (dielectric surface 107). In the embodiment shown, the feature 112 is a via. The via has a bottom formed by the conductive surface 105 and sidewalls formed by the dielectric surface 107.

The dielectric material 106 and the dielectric surface 107 of the dielectric material 106 comprises any suitable dielectric material. In some embodiments, the dielectric material 106 and the dielectric surface 107 comprises one or more of silicon nitride (SiN_(x)), silicon oxide (SiO_(x)), silicon oxynitride (SiO_(x)N_(y)), hafnium oxide (HfO_(x)) or combination thereof.

The conductive material 104 and the conductive surface 105 of the conductive material 104, comprises any suitable conductive material. In some embodiments, the conductive material 104 and the conductive surface 105 of the conductive material 104 comprises one or more of titanium (Ti), aluminum (Al), titanium nitride (TiN), titanium aluminide (TiAl), tantalum nitride (TaN), silicon (Si), tungsten (W), tungsten carbo nitride (WC_(x)N_(y)), cobalt (Co) or combinations thereof.

Referring to FIG. 2, the method 200 is performed in a process chamber or in a region (or station) of a batch process chamber. In some embodiments, the method 200 includes an optional pretreatment process 205. In some embodiments, the pretreatment process 205 comprises polishing, etching, reducing, oxidizing, hydroxylating, annealing and/or baking the substrate 100.

In some embodiments, as shown in method 100 and in FIG. 3, an optional nucleation layer 130 is formed on the substrate surface 102 prior to exposure to the first process condition 112. In some embodiments, the substrate surface 102 is not exposed to air between formation of the nucleation layer 130 and the first process condition 112.

In other embodiments, metal precursor may form another suitable metal film. Suitable metal films include, but are not limited to, films including one or more of cobalt (Co), molybdenum (Mo), tungsten (W), tantalum (Ta), titanium (Ti), ruthenium (Ru), rhodium (Rh), copper (Cu), iron (Fe), manganese (Mn), vanadium (V), niobium (Nb), hafnium (Hf), zirconium (Zr), yttrium (Y), aluminum (Al), tin (Sn), chromium (Cr), lanthanum (La), iridium (Ir), or any combination thereof. The metal precursor selected for the other metal films of some embodiments comprises or consists essentially of a fluorine-free metal halide.

Referring to FIG. 2, at process 210, the method 200 comprises three sub-processes. The skilled artisan will recognize that more or less than three sub-processes can be included in the process 210 and the disclosure is not limited to the process illustrated. The process 210 comprises sequentially exposing the substrate 100 having the dielectric surface 107 and the conductive surface 105 to a first process condition 212 to deposit a fluorine-free metallic tungsten film 120, an optional plasma treatment 214 and a second process condition 216 to deposit a tungsten film 140.

At process 212, the substrate 100 is exposed to the first process condition. As used in this manner, a “process condition” is any parameters used to deposit a predetermined film (e.g., precursor, flow rate, pressure, temperature). In some embodiments, the first process condition selectively deposits the fluorine-free tungsten-containing film on one surface preferentially relative to a second surface. FIG. 1 illustrates a selective deposition process in which the fluorine-free tungsten-containing film 120 is deposited selectively on the conductive surface 105 relative to the dielectric surface 107. As used in this manner, “selectivity”, “selectively” and the like, refer to a process that deposits at a faster rate on the stated surface relative to the adjacent surfaces. In some embodiments, the selective deposition conformally deposits in a structure having an aspect ratio greater than or equal to 2:1 or 4:1. In some embodiments, the first process condition comprises an Atomic Layer Deposition (ALD) process. In some embodiments, the ALD process deposits the fluorine-free metallic tungsten film 120 selectively on the conductive surface 105 relative to the dielectric surface 107.

One or more embodiments of the disclosure are directed to methods with high deposition rate for fluorine-free metallic tungsten films 120. Some embodiments use fluorine-free tungsten precursors to increase selectivity and/or deposition rate. Some embodiments provide high selectivity fluorine-free tungsten deposition with high throughput ALD processes. In some embodiments, the ALD process comprises sequentially exposing the substrate 100 to a fluorine-free tungsten precursor to deposit the fluorine-free tungsten-containing film, optionally purging the fluorine-free tungsten precursor and exposing the fluorine-free tungsten-containing film to a first reducing agent to form the fluorine-free metallic tungsten film 120.

In some embodiments, the fluorine-free tungsten precursor comprises a tungsten halide, a tungsten oxyhalide, a tungsten hydrohalide or combinations thereof. In some embodiments, the fluorine-free tungsten precursor consists essentially a tungsten halide or a tungsten oxy-halide. As used in this specification and the appended claims, the term “consists essentially of” means that the active (or reactive) species comprises greater than or equal to 95%, 98%, 99% or 99.5% of the stated species on a molar basis. In some embodiments, the tungsten halide comprises tungsten pentachloride (WCl₅), tungsten hexachloride (WCl₆), tungsten pentabromide (WBr₅), tungsten hexabromide (WBr₆) or combinations thereof. In some embodiments, the tungsten oxyhalide precursor comprises tungsten oxytetrachloride (WOCl₄), tungsten dichloride dioxide (WO₂Cl₂) or combinations thereof. In some embodiments, the fluorine-free tungsten precursor comprises tungsten pentachloride (WCl₅), tungsten hexachloride (WCl₆), tungsten oxytetrachloride (WOCl₄), tungsten dichloride dioxide (WO₂Cl₂), tungsten pentabromide (WBr₅), tungsten hexabromide (WBr₆) or combinations thereof. In other embodiments, the first process condition comprises a tungsten precursor selected from the group consisting of fluorine free tungsten halide precursors or chlorine-free tungsten halide precursors, such as tungsten pentabromide (WBr₅) or tungsten hexabromide (WBr₆).

In some embodiments, the fluorine-free tungsten precursor comprises a carrier gas. In some embodiments, an inert gas used as the carrier gas for the fluorine-free tungsten precursor. In some embodiments, the carrier gas comprises helium, neon, argon, nitrogen, krypton, xenon or combinations thereof. In some embodiments, argon is used as a carrier gas for the fluorine-free tungsten precursor.

In some embodiments, the substrate 100 is exposed to the fluorine-free tungsten precursor at a concentration in a range of from 100 sccm to 700 sccm, from 100 sccm to 600 sccm, from 100 sccm to 500 sccm, from 100 sccm to 400 sccm, from 100 sccm to 300 sccm, from 100 sccm to 200 sccm, from 200 sccm to 700 sccm, from 200 sccm to 600 sccm, from 200 sccm to 500 sccm, from 200 sccm to 400 sccm, from 200 sccm to 300 sccm, from 300 sccm to 700 sccm, from 300 sccm to 600 sccm, from 300 sccm to 500 sccm, from 300 sccm to 400 sccm, from 400 sccm to 700 sccm, from 400 sccm to 600 sccm, from 400 sccm to 500 sccm, from 500 sccm to 700 sccm, from 500 sccm to 600 sccm or from 600 sccm to 700 sccm.

In some embodiments, the fluorine-free tungsten precursor is solid or liquid. In some embodiments, the fluorine-free tungsten precursor is held in an ampoule. In some embodiments, a flow of the carrier gas passes through the ampoule and brings the fluorine-free tungsten precursor along to the substrate surface 100. As used herein, the flow rate of the fluorine-free tungsten precursor is the flow rate of the carrier gas including the fluorine-free tungsten precursor.

In some embodiments, the fluorine-free tungsten precursor comprises a co-flown reactant. In some embodiments, the co-flown reactant comprises a hydrogen containing gas. In some embodiments, the co-flown reactant comprises a reducing agent. In some embodiments, the co-flown reducing agent comprises H₂, SiH₄, Si₂H₆, Si₄H₁₂, NH₃, N₂H₄ or combinations thereof. In one or more embodiments, the fluorine-free tungsten precursor comprises the co-flown reducing agent at a concentration in a range of from 500 sccm to 7000 sccm, from 500 sccm to 6000 sccm, from 500 sccm to 5000 sccm, from 500 sccm to 4000 sccm, from 500 sccm to 3000 sccm, from 500 sccm to 2000 sccm, from 500 sccm to 1000 sccm, from 1000 sccm to 7000 sccm, from 1000 sccm to 6000 sccm, from 1000 sccm to 5000 sccm, from 1000 sccm to 4000 sccm, from 1000 sccm to 3000 sccm, from 1000 sccm to 2000 sccm, from 2000 sccm to 7000 sccm, from 2000 sccm to 6000 sccm, from 2000 sccm to 5000 sccm, from 2000 sccm to 4000 sccm, from 2000 sccm to 3000 sccm, from 3000 sccm to 7000 sccm, from 3000 sccm to 6000 sccm, from 3000 sccm to 5000 sccm, from 3000 sccm to 4000 sccm, from 4000 sccm to 7000 sccm, from 4000 sccm to 6000 sccm, from 4000 sccm to 5000 sccm, from 5000 sccm to 7000 sccm, from 5000 sccm to 6000 sccm or from 6000 sccm to 7000 sccm. In some embodiments, the fluorine-free tungsten precursor comprises hydrogen (H₂) at a concentration in a range of from 500 sccm to 7000 sccm,

In one or more embodiments, the co-flown reducing agent with fluorine-free tungsten precursor has substantially no CVD tungsten film growth. As used in this manner, the term “substantially no CVD” means that less than or equal to 5%, 2%, 1% or 0.5% of the fluorine-free tungsten film is formed through gas-phase reactions, on a volume basis. In some embodiments, substantially no CVD means no co-flown reactant during ALD deposition of the fluorine-free tungsten containing film. Without being bound by any particular theory of operation, it is believed that without enough reducing agent, the fluorine-free tungsten precursor is not reduced completely to metallic tungsten. It is believed that the co-flown reducing agent enables the fluorine-free tungsten precursor to thermally decompose into different derivatives of the fluorine-free precursor that significantly reduces more when exposed to the first reducing agent.

In some embodiments, the fluorine-free tungsten precursor consists of, or consists essentially of, a metallic tungsten precursor gas, a reactant gas, and a carrier gas. In some embodiments, the fluorine-free tungsten precursor consists of, or consists essentially of a chlorine-free, fluorine-free tungsten halide precursor, a hydrogen containing gas, and an inert gas.

In some embodiments, the fluorine-free tungsten film is deposited at a suitable temperature. In some embodiments, the suitable temperate is a temperature in a range of from 15° C. to 450° C., from 15° C. to 300° C., from 15° C. to 150° C., from 15° C. to 50° C., from 50° C. to 450° C., from 50° C. to 300° C., from 50° C. to 150° C., from 150° C. to 450° C., from 150° C. to 300° C. or from 300° C. to 450° C. In some embodiments, the substrate 100 is exposed to the fluorine-free tungsten precursor and the co-flown reducing agent at a temperature in a range of from 15° C. to 450° C. In some embodiments, substrate 100 is exposed to the fluorine-free tungsten precursor and a hydrogen (H₂) at a temperature in a range of from 15° C. to 450° C.

In some embodiments, the fluorine-free tungsten precursor and co-flown reducing agent increases the selectivity for conductive material relative to dielectric material. In some embodiments, the fluorine-free tungsten precursor and co-flown reducing agent increase the deposition rate with comparable film performance (e.g., step coverage, gap filling).

In some embodiments, the fluorine-free tungsten-containing film is substantially free of tungsten metal. As used in this manner, the term “tungsten metal” refers to zero valent tungsten atoms in the tungsten-containing film. As used in this manner, the term “substantially free of tungsten metal” means that less than or equal to 5%, 2%, 1% or 0.5% of the tungsten atoms in the tungsten-containing film are zero valent tungsten atoms. In some embodiments, the flow rates of the fluorine-free tungsten precursor and the co-flown reducing agent are configured to provide a fluorine-free tungsten-containing film substantially free of tungsten metal.

In some embodiments, the fluorine-free tungsten precursor is purged before exposing the substrate to the first reducing agent. The purging can be any suitable purge process that removes unreacted fluorine-free metal precursor, reaction products and by-products from the process region. The suitable purge process includes moving the substrate 100 through a gas curtain to a portion or sector of the processing region that contains none or substantially none of the reactant. In one or more embodiments, purging the processing region comprises applying a vacuum. In some embodiments, purging the processing region comprises flowing a purge gas over the substrate 100. In some embodiments, the purge process comprises flowing the same inert gas that is used as the carrier gas for the fluorine-free tungsten precursor. In one or more embodiments, the purge gas is selected from one or more of nitrogen (N₂), helium (He), and argon (Ar).

In some embodiments, the fluorine-free tungsten-containing film is reduced to a fluorine-free metallic tungsten film 120. Stated differently, in some embodiments, the fluorine-free tungsten-containing film is converted to the fluorine-free metallic tungsten film 120 by treating the fluorine-free tungsten-containing film that is substantially free of tungsten metal with the first reducing agent.

In one or more embodiments, the first process condition includes the first reducing agent that is reactive with the tungsten precursor. The first reducing agent (also referred to as a first reductant) comprises a reactive gas, such as a hydrogen-containing gas, such as hydrogen (H₂) or ammonia (NH₃) or hydrazine N₂H₄).

In one or more embodiments, the first reducing agent comprises hydrogen (H₂), silane (SiH₄), disilane (Si₂H₆), trisilane (Si₃H₈), tetrasilane (Si₄H₁₀), ammonia (NH₃), hydrazine (N₂H₄) or combinations thereof. In some embodiments, the first reducing agent comprises a carrier gas. In some embodiments, the carrier gas is an inert gas. In some embodiments, the inert gas comprises argon (Ar), helium (He), nitrogen (N₂) or combinations thereof. In some embodiments, the fluorine-free tungsten-containing film is exposed to the first reducing agent at a concentration in a range of from 500 sccm to 7000 sccm, from 500 sccm to 6000 sccm, from 500 sccm to 5000 sccm, from 500 sccm to 4000 sccm, from 500 sccm to 3000 sccm, from 500 sccm to 2000 sccm, from 500 sccm to 1000 sccm, from 1000 sccm to 7000 sccm, from 1000 sccm to 6000 sccm, from 1000 sccm to 5000 sccm, from 1000 sccm to 4000 sccm, from 1000 sccm to 3000 sccm, from 1000 sccm to 2000 sccm, from 2000 sccm to 7000 sccm, from 2000 sccm to 6000 sccm, from 2000 sccm to 5000 sccm, from 2000 sccm to 4000 sccm, from 2000 sccm to 3000 sccm, from 3000 sccm to 7000 sccm, from 3000 sccm to 6000 sccm, from 3000 sccm to 5000 sccm, from 3000 sccm to 4000 sccm, from 4000 sccm to 7000 sccm, from 4000 sccm to 6000 sccm, from 4000 sccm to 5000 sccm, from 5000 sccm to 7000 sccm, from 5000 sccm to 6000 sccm or from 6000 sccm to 7000 sccm.

At 214, in some embodiments, the first reducing agent is optionally purged from the processing region. Purging the processing region removes unreacted reactant, reaction products and by-products from the area adjacent the substrate surface 100. The purge process can be any suitable purge process that removes unreacted first reducing agent from the process region. In some embodiments, the purge process can be the same or different process as the fluorine-free tungsten precursor purge process.

In one or more embodiments, the ALD process cycle comprises exposing a substrate surface to a fluorine-free tungsten precursor comprising co-flowing hydrogen (H₂) at a dose in a range of from 500 sccm to 7000 sccm to deposit a fluorine-free film, optionally purging fluorine-free tungsten precursor, exposing the fluorine-free film to H₂ at a dose in a range of from 0 sccm to 7000 sccm, and optionally purging H₂.

In some embodiments, the ALD process cycle is repeated until the fluorine-free metallic tungsten film 120 has a thickness in a range of from 20 Å to 60 Å, from 30 Å to 60 Å, from 40 Å to 60 Å, from 50 Å to 60 Å, from 20 Å to 50 Å, from 30 Å to 50 Å, from 40 Å to 50 Å, from 20 Å to 40 Å, from 30 Å to 40 Å or from 20 Å to 30 Å.

The substrate 100 temperature of some embodiments is maintained throughout the ALD process 110. In some embodiments, the substrate 100 is maintained at a temperature in a range of from 15° C. to 450° C., from 50° C. to 450° C., from 100° C. to 450° C., from 200° C. to 450° C., from 300° C. to 450° C., from 400° C. to 450° C., from 15° C. to 350° C., from 50° C. to 350° C., from 100° C. to 350° C., from 200° C. to 350° C., from 300° C. to 350° C., from 15° C. to 250° C., from 50° C. to 250° C., from 100° C. to 250° C., from 200° C. to 250° C., from 15° C. to 150° C., from 50° C. to 150° C. or from 100° C. to 150° C. during the ALD process 110.

ALD fluorine-free metallic tungsten film 120 in some embodiments replaces and/or reduces traditional high resistivity nucleation layers (e.g., SiH₄ or B₂H₆ ALD W 20-30 Å) and thick fluorine barrier (e.g., TiN 30-50 Å). In some embodiments, the fluorine-free metallic tungsten film 120 has low resistivity, excellent step coverage, superior fluorine barrier property, and can integrate with conventional tungsten fluoride (WF_(x)) based bulk tungsten fill. Some embodiments improve throughput while maintaining acceptable film performance or other metrics (e.g., non-uniformity, step coverage, particles).

The total flow into the process region according to some embodiments is the combined flow rates of the fluorine-free metal precursor and the first reducing agent. In some embodiments, a make-up gas is flowed into the process region and the fluorine-free metal precursor and the first reducing agent are added to the make-up gas flow stream. In some embodiments, the make-up gas flow stream is at a much larger flow rate than either the fluorine-free metal precursor or the first reducing agent. In some embodiments, the make-up gas flow stream has a flow rate greater than 10× the higher of the precursor flow or the first reducing agent flow. The skilled artisan would understand that the flow rate of a make-up gas does not change the ratio of the fluorine-free tungsten precursor to the first reducing agent. The make-up gas flow can change the overall concentration of the fluorine-free tungsten precursor and/or the first reducing agent. In some embodiments, the first process condition has a flow rate of the first reducing agent is in a range of from 5% to 70% of a flow rate of the fluorine-free tungsten precursor. In some embodiments, the fluorine-free tungsten precursor and the first reducing agent has a flow rate ratio in a range of from 10:1 to 1:2.5.

At process 215, the fluorine-free metallic tungsten film 120 is optionally treated with a plasma. In some embodiments, the plasma treatment causes thermal reduction of the fluorine-free metallic tungsten film 120. In some embodiments, the plasma is generated at a power in a range of from 100 W to 1500 W, from 100 W to 1200 W, from 100 W to 900 W, from 100 W to 600 W, from 100 W to 300 W, from 300 W to 1500 W, from 300 W to 1200 W, from 300 W to 900 W, from 300 W to 600 W, from 600 W to 1500 W, from 600 W to 1200 W, from 600 W to 900 W, from 900 W to 1500 W, from 900 W to 1200 W or from 1200 W to 1500 W. In some embodiments, the plasma treatment comprises hydrogen (H₂) plasma treatment, oxygen (O₂) plasma treatment, argon (Ar) plasma treatment or combinations thereof. In some embodiments, the hydrogen and oxygen plasma is configured to thermally reduce the fluorine-free metallic tungsten film 120 by radicals and ions.

At process 216, the fluorine-free metallic tungsten film 130 is exposed to a second process condition to deposit the tungsten film 140. In some embodiments, the second process is a chemical vapor deposition (CVD) process. The CVD process is configured to deposit and grow the tungsten film 140 on the fluorine-free metallic tungsten film 130. In some embodiments, the CVD process comprises exposing the fluorine-free metallic tungsten film 130 to a second tungsten precursor. In some embodiments, the feature 112 is filled in a bottom-up manner. As used in this manner, the term “bottom-up” means that most of the deposition occurs on the metallic tungsten film 130 initially, and then on the deposited tungsten film as the thickness grows, with little to no deposition on the sidewalls of the feature 112.

In some embodiments, the second tungsten precursor comprises a tungsten halide, tungsten oxyhalide, tungsten hydrohalide or combinations thereof. In some embodiments, the tungsten halide comprises fluorine atoms. In some embodiments, the tungsten fluoride comprises one or more of tungsten hexafluoride (WF₆) or tungsten pentafluoride (WF₅).

In some embodiments, the fluorine-free metallic tungsten film 130 is exposed to the second tungsten precursor at a concentration in a range of from 50 sccm to 500 sccm, from 50 sccm to 400 sccm, from 50 sccm to 300 sccm, from 50 sccm to 200 sccm, from 50 sccm to 100 sccm, from 100 sccm, to 500 sccm, from 100 sccm to 400 sccm, from 100 sccm to 300 sccm, from 100 sccm to 200 sccm, from 200 sccm to 500 sccm, from 200 sccm to 400 sccm, from 200 sccm to 300 sccm, from 300 sccm to 500 sccm, from 300 sccm to 400 sccm or from 400 sccm to 500 sccm. In some embodiments, the second tungsten precursor is flowed into the process region at a pressure in a rage of from 1 mTorr to 20 Torr, from 1 mTorr to 10 Torr, from 1 mTorr to 5 Torr, from 1 mTorr to 1 Torr, from 1 mTorr to 500 mTorr, from 500 mTorr to 20 Torr, from 500 mTorr to 10 Torr, from 500 mTorr to 5 Torr, from 500 mTorr to 1 Torr, from 1 Torr to 20 Torr, from 1 Torr to 10 Torr, from 1 Torr to 5 Torr, from 5 Torr to 20 Torr, from 5 Torr to 10 Torr or from 10 Torr to 20 Torr.

In some embodiments, the second tungsten precursor comprises a carrier gas. In some embodiments, an inert gas used as the carrier gas for the second tungsten precursor. In some embodiments, the carrier gas comprises helium, neon, argon, nitrogen, krypton, xenon or combinations thereof.

In some embodiments, the second tungsten precursor is solid, gas or liquid. In some embodiments, the second tungsten precursor is held in an ampoule. In some embodiments, a flow of the carrier gas passes through the ampoule and brings the second tungsten precursor along to the process region. As used herein, the flow rate of the second tungsten precursor is the flow rate of the carrier gas including the second tungsten precursor.

In some embodiments, the second tungsten precursor comprises a second reducing agent. In some embodiments, the second reducing agent is the same species as the first reducing agent. In some embodiments, the second reducing agent is a different species as the first reducing agent. The concentration of the second reducing agent can be the same or different from the first reducing agent concentration. In some embodiments, the second reducing agent comprises one or more of hydrogen (H₂), silane (SiH₄), disilane (Si₂H₆), trisilane (Si₃H₈), tetrasilane (Si₄H₁₀), hydrazine (N₂H₄) or ammonia (NH₃).

In some embodiments, the second tungsten precursor comprises the carrier gas and/or make-up gas. In some embodiments, the carrier gas and/or make-up gas is an inert gas. In some embodiments, the inert gas comprises argon (Ar), helium (He), nitrogen (N₂) or combinations thereof.

At process 218, in some embodiments, the second tungsten precursor is optionally purged from the processing region. Purging the processing region removes unreacted reactant, reaction products and by-products from the area adjacent the substrate surface 100. The purge process can be any suitable purge process that removes unreacted second tungsten precursor from the process region. In some embodiments, the purge process can be the same or different process as the fluorine-free tungsten precursor purge process.

In some embodiments, the fluorine-free metallic tungsten film 130 is exposed to the second tungsten precursor until the tungsten film 140 has a thickness in a range of from 0 Å to 1000 Å, from 50 Å to 1000 Å, from 100 Å to 1000 Å, from 200 Å to 1000 Å, from 500 Å to 1000 Å, from 800 Å to 1000 Å, from 0 Å to 800 Å, from 50 Å to 800 Å, from 100 Å to 800 Å, from 200 Å to 800 Å, from 500 Å to 800 Å, from 0 Å to 500 Å, from 50 Å to 500 Å, from 100 Å to 500 Å, from 200 Å to 500 Å, from 0 Å to 200 Å, from 50 Å to 200 Å, from 100 Å to 200 Å, from 0 Å to 100 Å, from 50 Å to 100 Å or from 50 Å to 100 Å.

In some embodiments, as illustrated in FIG. 1, the metallic tungsten film 140 is formed selectively on the conductive surface 105 over the dielectric surface 107. In some embodiments, the metallic tungsten film 140 fills the structure 112 in a gap fill process. The metallic tungsten film 240 of some embodiments deposits at a rate greater than or equal to twice a deposition rate of a substantially similar process without the first reducing agent in the first process condition.

In some embodiments, the substrate 100 is maintained at a temperature in a range of from 15° C. to 450° C., from 50° C. to 450° C., from 100° C. to 450° C., from 200° C. to 450° C., from 300° C. to 450° C., from 400° C. to 450° C., from 15° C. to 350° C., from 50° C. to 350° C., from 100° C. to 350° C., from 200° C. to 350° C., from 300° C. to 350° C., from 15° C. to 250° C., from 50° C. to 250° C., from 100° C. to 250° C., from 200° C. to 250° C., from 15° C. to 150° C., from 50° C. to 150° C. or from 100° C. to 150° C. during the ALD process condition 212 and the second process condition 216.

At decision point 220, a thickness of the tungsten film 140 is examined as part of method 100 of some embodiments. If the tungsten film 140 has reached a predetermined thickness, the method 100 ends or moves to an optional post-deposition process 230. If the predetermined condition(s) have not been met, the method 200 repeats the process 216.

The optional post-processing operation 230 can be, for example, a process to modify film properties (e.g., annealing) or a further film deposition process (e.g., additional ALD or CVD processes) to grow additional films. In some embodiments, the optional post-processing operation 230 can be a process that modifies a property of the deposited film. In some embodiments, the optional post-processing operation 230 comprises annealing the as-deposited film. In some embodiments, annealing is done at temperatures in the range of about 300° C., 400° C., 500° C., 600° C., 700° C., 800° C., 900° C. or 1000° C. The annealing environment of some embodiments comprises one or more of an inert gas (e.g., molecular nitrogen (N₂), argon (Ar)) or a reducing gas (e.g., molecular hydrogen (H₂) or ammonia (NH₃)) or an oxidant, such as, but not limited to, oxygen (O₂), ozone (O₃), or peroxides. Annealing can be performed for any suitable length of time. In some embodiments, the film is annealed for a predetermined time in the range of about 15 seconds to about 90 minutes, or in the range of about 1 minute to about 60 minutes. In some embodiments, annealing the as-deposited film increases the density, decreases the resistivity and/or increases the purity of the film.

In the foregoing specification, embodiments of the disclosure have been described with reference to specific exemplary embodiments thereof. It will be evident that various modifications may be made thereto without departing from the broader spirit and scope of the embodiments of the disclosure as set forth in the following claims. The specification and drawings are, accordingly, to be regarded in an illustrative sense rather than a restrictive sense. 

What is claimed is:
 1. A method comprising: exposing a substrate surface to a first process condition comprising a flow of a fluorine-free tungsten precursor and a flow of a first reducing agent to form a fluorine-free metallic tungsten film on the substrate surface to a first thickness; and exposing the fluorine-free metallic tungsten film to a second process condition comprising a flow of a second tungsten precursor to deposit a tungsten film.
 2. The method of claim 1, wherein the fluorine-free tungsten precursor comprises tungsten halides, tungsten hydrohalides, tungsten oxyhalides or combinations thereof.
 3. The method of claim 1, wherein the first reducing agent and the second reducing agent independently comprises one or more of hydrogen (H₂), silane (SiH₄), disilane (Si₂H₆), trisilane (Si₃H₈), tetrasilane (Si₄H₁₀) or ammonia (NH₃).
 4. The method of claim 1, wherein the fluorine-free tungsten precursor has a flow rate in a range of from 100 sccm to 700 sccm.
 5. The method of claim 1, wherein the fluorine-free tungsten precursor further comprises a co-flown reducing agent, the co-flown reducing agent has a flow rate in the range of 500 to 7000 sccm.
 6. The method of claim 1, wherein the first process condition comprises flowing the fluorine-free tungsten precursor and flowing the first reducing agent at a pressure in a range of from 15 psi to 30 psi.
 7. The method of claim 1, wherein the first thickness is in the range of 20 Å to 60 Å
 8. The method of claim 1 further comprising treating the fluorine-free metallic tungsten film with a plasma.
 9. The method of claim 8, wherein the plasma treatment causes thermal reduction of the fluorine-free metallic tungsten film.
 10. The method of claim 8, wherein the plasma is generated in a range of from 100 W to 1500 W.
 11. The method of claim 8, wherein the plasma treatment comprises Hydrogen (H₂) plasma treatment, Oxygen (O₂) plasma treatment, Argon (Ar) plasma treatment or combinations thereof.
 12. The method of claim 1, wherein the second tungsten precursor comprises a tungsten fluoride or derivative thereof.
 13. The method of claim 1, wherein the second process condition further comprises co-flowing a second reducing with the second tungsten precursor, the second reducing agent comprises one or more of hydrogen (H₂), silane (SiH₄), disilane (Si₂H₆), trisilane (Si₃H₈), tetrasilane (Si₄H₁₀) or ammonia (NH₃).
 14. The method of claim 1 further comprising pre-cleaning the substrate surface before exposing to the first process condition, the pre-cleaning comprises treating the substrate surface with a plasma.
 15. The method of claim 1, wherein one or more of the first process condition, plasma treatment or the second process condition are performed at a temperature in a range of from 15° C. to 450° C.
 16. The method of claim 1, wherein the substrate surface has a structure formed thereon having a bottom and sidewall, the bottom of the structure comprising a conductive surface and the sidewall of the structure comprising a dielectric surface.
 17. The method of claim 16, wherein the fluorine-free metallic tungsten film is deposited selectively on the bottom of the structure relative to the sidewall of the structure, the structure has an aspect ratio in a range of from 2:1 to 4:1.
 18. The method of claim 16, wherein the dielectric surface comprises one or more of a SiN_(x), SiO_(x), SiO_(x)N_(y), or combination thereof.
 19. The method of claim 16, wherein the conductive surface comprises TiN, TiAl, WC_(x)N_(y), W or combination thereof.
 20. A method comprising: exposing a substrate surface to a first process condition comprising a flow of a fluorine-free tungsten precursor and a flow of a first reducing agent to form a fluorine-free metallic tungsten film on the substrate surface to a first thickness; treating the fluorine free metallic tungsten film with a plasma; and exposing the plasma treated fluorine-free metallic tungsten film to a second process condition comprising a flow of a second tungsten precursor to deposit a tungsten film. 